If you are not having any effect with the scalpel tool, these could be reasons:
Ø Curves cannot be modified by the scalpel tool.

Ø Are the objects part of a group? Try ungrouping them and then scalpel them.

Ø Are the objects in a frozen overlay? Try selecting them, and if you get a warning about the objects being frozen, unfreeze that overlay.

Ø Fractal lines are cut along the guideline, not along the actual fractal.